The long-term objective is to achieve understanding, at the molecular level, of the mechanism or mechanisms by which juvenile hormone (JH) regulates the synthesis of specific proteins and, through this, plays a key role in control of development and reproduction of insects. This is being attacked through study of how JH regulates expression of the genes for vitellogenin (Vg) in the fat body of migratory locusts. In work already completed, locust Vg has been characterized, as well as the cytological and biochemical changes that occur in the fat body during stimulation by the JH analog, methoprene, and the general dose-response and kinetic characteristics of the response. Although both female and male adult fat body contain JH receptors and replicate DNA in response to methoprene, the Vg genes are activated in only the female tissue, as a result of developmental gene programming. Vg mRNA has been characterized, and cDNA and genomic DNA clones for portions of Vg genes have been isolated. In the coming grant period, we intend to isolate in clones the remainder of the locust gene or genes for Vg, as well as genes for other control proteins which are not regulated by JH, and compare the structures of these, including the nucleotide sequences of regions likely to be involved in regulation. We shall study the developmental, sex-limited programming of the Vg genes for hormone-responsiveness by investigating specific sequence methylation and protein binding. We shall measure the early rates of synthesis of Vg mRNA, Vg and other proteins and test the effects of specific inhibitors on these in order to deduce causal relationships. We shall characterize the cytoplasmic JH receptor and measure receptor levels in the nucleus during hormonal stimulation. Results wil be interpreted as a model system for understanding hormonal regulation of animal development through control of gene activity.